This application is the National Stage of PCT/DE2007/000535 filed on Mar. 23, 2007, which claims priority under 35 U.S.C. §119 of German Application No. 10 2006 015 586.6 filed on Apr. 4, 2006. The international application under PCT article 21(2) was not published in English.
The present invention relates to pin bosses of a piston for an internal combustion engine, having pin bores for mounting a piston pin in the shape of a circular cylinder.
Pin bosses of a piston for an internal combustion engine are known from the Offenlegungsschrift [examined patent application published for public scrutiny] DE 44 41 150 A1, which have a pin bore, in each instance, whose zenith-side ovality and nadir-side ovality, proceeding from the center of the bore, increase radially inward. It is a disadvantage, in this connection, that the center of the bore is configured in the shape of a circular cylinder, so that lubrication of the piston pin is deficient in the region of the center of the bore, and here, there is the risk of damage to the pin bore and to the piston pin, specifically during a cold start.
It is known from the PCT application WO 2004/008006 A1, to provide the pin bores of the pin bosses with a zenith-side ovality, radially on the outside. But neither the center of the bore nor the nadir region of the pin bore that lies radially on the inside have an oval cross-section shape, and this brings with it not only lubrication problems of the piston pin in the region of the center of the bore, but the further disadvantage that in the case of tensile stress on the piston pin, during which its center part experiences deformation in the direction facing away from the piston crown, the piston pin is pressed onto the inner nadir region of the pin bore, and this can lead to damage to this bore region and to pin boss friction, particularly during a cold start.
It is the task of the invention to avoid the stated disadvantages of the state of the art.
This task is accomplished with pin bores that have a zenith-side ovality in the region of the center of the bore, whereby the zenith-side ovality of the pin bores increases radially inward and radially outward, proceeding from the center of the bore, and furthermore, the nadir-side ovality increases radially inward, proceeding from the center of the bore. In this connection, the shape of the pin bore is adapted to every temperature-related and stress-dependent deformation of the piston and of the piston pin. Furthermore, a gap remains between the piston pin and the pin bore, when the piston pin is unstressed and therefore not deformed, in the center of the bore, because of the residual ovality of the zenith, in which gap lubricant oil collects, which guarantees good lubrication of the pin, particularly during a cold start.
Practical embodiments of the invention are the object of the dependent claims.
Some exemplary embodiments of the invention will be described in the following, using the drawings. These show:
The nadir 8 of the pin bore 3 has a region 9 that lies radially on the outside, proceeding from the center 7 of the bore, which region is configured in the shape of a semicircle, in section, crosswise to the pin bore 3. In addition, the nadir 8 has a region 10 that lies radially on the inside, whose ovality increases, in linear manner, proceeding from the center 7 of the bore. In this connection, the ovalities of the regions 5, 6, and 10 of the pin bore 3 can increase in different measure.
The ovality of the regions 5, 6, and 10 of the pin bore 3 is shown with great magnification in
13 refers to a top view of the outer face surface 11 of the pin boss 1, which shows the upper edge 14 of the pin bore 3, with maximal ovality of the region 5 of the zenith 4 of the pin bore 3 that lies radially on the outside, the pin bore 3 in the region 15 of the center 7 of the bore with zenith-side residual ovality, the nadir region 9 of the pin bore 3 that lies radially on the outside, and has the shape of a semicircle, and, with a broken line, the lower edge 16 of the pin bore 3, with maximal, nadir-side ovality, which lies radially on the inside.
In
In this connection, the shape of the pin bore 3 is adapted to every stress-dependent deformation of the piston pin. If the piston pin is deformed in accordance with the lines 17, 17′, because of the pressure stress that occurs during the explosion cycle, the piston pin lies against the ovality of the zenith region 6 that increases radially inward from the center 7 of the bore, thereby preventing material stresses from proceeding from the zenith-side edge 20 of the pin bore 3 that lies radially on the inside, which stresses, together with the very great pressure stresses that occur, particularly in the case of a diesel engine, can lead to damage to the piston crown and to the combustion bowl disposed in the piston crown.
In the case of a deformation of the piston pin due to tensile stress on the piston pin that proceeds from the connecting rod, in accordance with the lines 18, 18′, the piston pin lies against the ovality of the nadir region 10, which lies radially on the inside and increases from the center 7 of the bore. In this way, it is prevented that a material stress is exerted by the piston pin on the edge 16 of the nadir region of the pin bore that lies radially on the inside, which stress can lead to damage to the inner region of the pin bore. However, direct contact between piston pin ad pin bore 3 is avoided, in this connection, so that a sufficiently large gap always remains between piston pin and pin bore, in which lubricant oil can collect and ensure sufficient lubrication of the piston pin.
The residual ovality of the zenith 4 of the pin bore 3 that is present in the center 7 of the bore has the advantage that here, a gap forms between the unstressed piston pin 19, 19′ and the zenith 4 of the bore 3, in which gap lubricant oil collects, which guarantees good lubrication of the piston pin, particularly during a cold start, if the piston pin deforms in this connection, as shown by means of the lines 17, 17′.
Since the zenith region 15 of the pin bore 3 according to
Number | Date | Country | Kind |
---|---|---|---|
10 2006 015 586 | Apr 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/DE2007/000535 | 3/23/2007 | WO | 00 | 10/20/2008 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2007/115527 | 10/18/2007 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4124010 | Fiedler | Nov 1978 | A |
5112145 | MacGregor | May 1992 | A |
5653156 | Issler et al. | Aug 1997 | A |
5746169 | Issler et al. | May 1998 | A |
5934766 | Feigel et al. | Aug 1999 | A |
7107893 | Weinkauf et al. | Sep 2006 | B2 |
7305960 | Zvonkovic | Dec 2007 | B2 |
7647863 | Issler et al. | Jan 2010 | B2 |
20070204746 | Issler et al. | Sep 2007 | A1 |
Number | Date | Country |
---|---|---|
2 152 462 | Apr 1973 | DE |
30 36 062 | Apr 1982 | DE |
41 11 368 | Jan 1992 | DE |
43 27 772 | Feb 1995 | DE |
44 41 150 | May 1996 | DE |
102 31 233 | Feb 2004 | DE |
10 2004 008 097 | Sep 2005 | DE |
1 405 959 | Sep 1975 | GB |
62-184274 | Aug 1987 | JP |
10-103513 | Apr 1998 | JP |
11-303993 | Nov 1999 | JP |
2004-028025 | Jan 2004 | JP |
WO 9607841 | Mar 1996 | WO |
WO 03098078 | Nov 2003 | WO |
WO 2004008006 | Jan 2004 | WO |
WO 2007025733 | Mar 2007 | WO |
Number | Date | Country | |
---|---|---|---|
20090114087 A1 | May 2009 | US |